University Honors

Mangroves are woody plants that thrive in the tropics and subtropics inestuaries—regions where freshwater and saltwater meet. Bacteria associated with mangrovepeat (plant material unable to decay due to anoxic and acidic environments) with recalcitrantnutrients play an important role in sequestering carbon. In a previous study by Costa et al.,bacteria isolated from collection sites at La Paz, Baja California Sur, Mexico, have beenshown to sequester carbon in peat aged approximately 5,000 years. Microbial communityvariation with depth was observed. While microbes have cycled nitrogen deposits, there islittle sign of remineralized carbon back into the ecosystem. Nevertheless, the diversity ofbacteria differs at each peat level, giving insight into peat carbon density, which is relativelystable. Assuming similar anoxic conditions with recalcitrant material, distinct bacterialcommunities with decreased carbon turnover according to peat depth are hypothesized in amangrove forest in Celestun, Yucatan, Mexico. Samples were collected at various depths toexamine microbial communities in different sediment types. Microbial DNA was extractedand purified, and the V3 and V4 regions of the 16S rRNA gene were PCR amplified. Resultsrevealed distinct phyla according to sediment type and depth, including Chloroflexi in deeperpeat deposits and Pir4 in shallower peat deposits, leaf litter, and roots. The microbialcommunity appears to be remineralizing carbon at a slower rate, allowing for peat toaccumulate carbon over time.